Monophonic electronic musical instrument

ABSTRACT

A monophonic electronic music synthesizer in which keying signals are collected on common note busses and common octave busses with a low note lockout circuit and a low octave lockout circuit to provide unambiguous high note select. Keying signals on note and octave busses are encoded in binary encoding circuits and the resultant binary note and octave words stored in note and octave word latches. Decoding gates fed by the latches gate the high note tone signal and the high octave tone signal after frequency division. Complete circuitry for a synthesizer system, including some alternate embodiments, is shown and described.

United States Patent Schreier 1 Aug. 12, 1975 [54] MONOPHONIC ELECTRONIC MUSICAL 1 3,806,624 4/1974 Kniepkamp et a1 84/LO3 INSTRUMENT 3,828,643 8/1974 Morez 84/101 X w f d R b S h 3,842,702 10/1974 Tsundoo.. 84/101 {75] Inventor: 11 or ay urn c reier,

Bensenvme L -OTHER PUBLICATIONS R. W. Burhans, Digital Tone Synthesis, Journal of [73] Asslgnee Hammond Corporanon chlclgo the Audio Engineering Society, Vol. 19, No. 8, Sept.

1971, pp. 660663. [22] Filed: Mar. 4, 1974 Primary ExaminerStephen J. Tomsky [211 Appl' 447905 Assistant Examiner-Stanley J. Witkowski Attorney, Agent, or FirmLowell C. Bergstedt [52] US. Cl. 84/l.0l; 84/103; 84/D1G. 2;

84/D1G. 20 ABSTRACT 1 1 Gloh Gloh A monophonic electronic music synthesizer in which [58] Field of Search 84/l.01l.03, k ying signals are collected on common note busses [316- 20 and common octave busses with a low note lockout circuit and a low octave lockout circuit to provide un- 1 References Cited ambiguous high note select. Keying signals on note UNlTED STATES PATENTS and octave busses are encoded in binary encoding cir- 3,509,262 4 1970 Munch, Jr 84/101 Cults the resultant binary note and Octave wofds 3,515,792 6/1970 Deutsch ..s4 1.03 Stored 1 and Octave Word h Decodmg 3,594,487 7/1971 Jones, Jr.. 84/101 X gates fed by the latches gate the high note tone signal 3,610,799 10/1971 Watsonm. 84/101 and the high octave tone signal after frequency divi- 3,647,929 3/1972 Nlilde, Jr 84/].01 ion Complete Circuitry for a synthesizer ystem in- 3,760,358 9/1973 lsn et a1. 84/1 .01 X eluding some alternate embodiments is Shown and 3,771.406 11/1973 wheelwrightm 84/1.01 X scribed 3,801,721 4/1974 Bunger 84/].24 X 3,806,623 4/1974 Yamada 84/101 15 Claims, 22 Drawing Figures OCTAVE I KEY DOWN FT coLLEcT DETECTOR 7/ LOW OCTAVE I flfi 8/ LOCKOUT T I 11 290I Low NOTE 4/ LOCKOUT 29/L 9/ OCTAVE 0 NOTE coLLEcT COLLECT OCTAVE BINARY 360 ENcoDER 350 MONOPHONIC 02: f39/ 37/ OCTAVE 340 UTPUT 3.90 O D WORD 370 20/ 2/0 2// 220 LATCHES LATCHE 7 ma //0 N 3,2 m I L 7 TOP NoTE YFREQUENQX ocTAvE PITCH voLTAeE voLTAeE gag/ET ZECEDE mvlDERs DECODE AND CONTROLLED CONTROLLED T s ATE vi I) (5 S WAVEFORM FILTER AMPLIFIER 22/ C VOLTAGE 24/ 320 voLTs 350 27/ 28/ CONTROLLED 240 In PER 35/ 200 OSCILLATOR ocTAvE 430 AMPLIFIER 280 25/ ENVELOPE ENVELOPE VIBRATO 237 1' GENERATOR GENERATOR AND LEGATO -267 1 270 PORTALENTO PULSE 01 cm s 1250 GENERATOR 1 26/ PATENTED 'AUG 1 2 I975 SHEET Nmm PATENTED AUG 1 2 I975 SPEET mOP mwZww M902 MCI;

mim-

m WW5. PG. mum. W Cm. 0 m8 mmu PATENTE Auci 21975 SHEET 2 QE 5%. 8% A JJ r may; 8% m 8% mvo PATENTEB Ausi 2197s SHEET 12 KEYBOARD llb/O FIG.3 FIG.4

30 FIG.|4 FIG.6 400 LOW OCTAVE 2 FIG.7 FIG.8 FIG.9

LOOKOUT FIG.|0 FIG.

2 FIG. [5 /T390 LOW NOTE OcTAvE CK LO OUT COLE: L70

9/ FIG. l9 NOTE COLLECT 2 FIG-l3 FIG.3 F|G.l7 90 i} 5'3 FIG.|8

a0 70 NOTE OCTAVE ,5

COLLECT COLLECT FIG I6 NOTE -5 OcTAvE 5' LATCHES LATCHES NOTE FREQUENCY OCTAVE men NOTE GATES O|v| ERs ATEs TONE SIGNAL FROM TOP OcTAvE /70 530 TONE GENERATOR 540 LOW NOTE NOTE 550 KEYBOA D LOCKOUT BINARY ENCODER /0 NOTE WORD 5560 FIG. 20 LATCHES /00 580 am TOP OCTAVE FREQUENCY DECODE HIGH NOTE TONE TONE GENERATOR DIVIDERS GATES SIGNAL OUT PATENTEU AUG I 21975 OW 3,898,905

FROM NOTE FROM OCTAVE WORD LATCHES WORD LATCHES ll D.C. 5 c 600 NOTE OCTAVE DECODER DECODER 1 /00 TOP 5. 20 OCTAVE NOTE FREQUENCY OCTAVE TONE 0.0. D.C. GENERATOR GATES DIV'DEIRS GATES HIGH NOTE TONE SIGNAL 0'0 6/0 2525 FIG. 2|

OCTAVE 4 B5 D60 *5 EFD G D60 HIGH NOTE SIGNAL TO FREQUENCY DIVIDERS I TO VOLTS PER OCTAVE CIRCUIT EFF? FIG 22 MONOPHONIC ELECTRONIC MUSICAL INSTRUMENT FIELD OF THE INVENTION This invention relates to monophonic electronic mu sical instruments and more particularly to electronic music synthesizers for simulating various orchestral instrument voices and for producing unique musical and non-musical sounds. 1

DESCRIPTION OF PRIOR ART Electronic music synthesizers are typically monophonic instruments which involve generating a tone signal of a selected frequency and waveshape and subjecting the tone signal to controlled frequency modulation. controlled filtering. and controlled amplification to produce the desired musical effect. By providing a variety of wave-shapes and dynamic changes in frequency. filtering, and amplification. as well as controlled introduction of noise. various types of orchestral instrument voices can be authentically simulated and unique sounds not made by familiar musical instruments can be generated.

The commercially available synthesizers marketed under the trade names Moog and ARP have generally similar system characteristics. A keyboard. which is generally similar to a piano or organ keyboard. is provided with keyswitches for each key having a plurality of contact pairs for diffcrentcontrol functions. One contact pair per key is employed to ground ajunction in a precision resistor divider string fed by a constant current source to develop a voltage at the output of the current source which is linearly related to the position of the actuated key on the keyboard. Other contact pairs are employed to produce a keydown" signal. i.e.. a signal that at least one key is depressed. and a legato pulse" signal. i.e.. a signal that a new effective key is depressed. The constant current source and precision resistor divider string comprise a volts store or memorize the voltage signal so that it is available even if the actuated key is released. The memorized voltage signal is fed to a circuit which converts the linear volts per octave signal to an exponential signal. This exponentially varying signal has the proper characteristic to control a voltage-controlled oscillator which thus produces an output tone signal corresponding to the note associated with the actuated key on the keyboard. The output tone signal is fed to a voltagecontrolled filter which may be programmed to have various frequency response characteristics including dynamic characteristics produced by a circuit which produces voltage control envelopes of various types. Then the filtered signal is furtherprocessed in a voltage-controlled amplifier which may be programmed via a circuit which produces various types of voltage control envelopes to amplitude modulate the signal. Moreover. the voltage-controlled oscillator itself may be subjected to various types of modulation to produce vibrato and other musical effects.

Several years ago. the Wurlitzer Company introduced a synthesizer as an optional add-on feature to several of its electronic organ models. The synthesizer was controlled via a two-octave keyboard separate from the solo keyboard of the organ and thus the player could not play the synthesizer integrally with upper manual solo voices. The Wurlitzer synthesizer employs a single oscillator-parallel divider chain approach to generating the top octave tone signals. These top oetave tone signals are directly fed to a first priority latching network which is coupled to one octave of keyboard switches. The top octave tone signals are also sent through individual frequency dividers to generate the next lowest octave of tones and then are fed to a second priority latching network. A complex arrangement of parallel frequency dividers fedby the two pri- 1 companies have chosen to integrate the type of tone generation system used in Moog and ARP units and to control the tone generation system via additional contacts per key.

SUMMARY OF THE INVENTION This invention proceeds from the system disclosedin copending Schrecongost patent application, Ser. No. 448.020 filed Mar. 4. I974 and provides an electronic music synthesizer in which unambiquous high note select is accomplished by employing a low note lockout circuit as well as an octave lockout circuit. This approach enables the note and octave keying signal information to be encoded into binary note and octave words which are then stored in latches and used to control decode gates for top octave tone signals and also octave tone signals after frequency division.

This invention involves numerous novel circuit designs to accomplish a complete synthesizer system. the advantages of which will be apparent from the detailed description below.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a generalized block schematic diagram of a synthesizer system employing this invention.

FIG. 2 is a block schematic diagram of a synthesizer system in accordance with one embodiment of this invention.

FIGS. 3 through 11 together comprise a circuit schematic diagram of a synthesizer system according to 'FlG. 2. 7

FIG. 12 illustrates the manner in which FIGS. 3

through II are to be assembled into a system sche- FIG. 16 is a block diagram of another alternate embodiment of this invention.

FIGS. 17 and 18 are circuit schematic diagrams which fit together with FIG. 3 and either FIG. or FIG. 14 to disclose the alternate embodiment of FIG. I6.

FIG. 19 illustrates how FIGS. I7 and I8 fit into an overall circuit schematic.

FIG. 20 is a block diagram of another alternate embodiment of this invention.

FIG. 2I is a block diagram of another alternate embodiment of this invention.

FIG. 22 is a partial circuit schematic diagram of the alternate embodiment of FIG. 2].

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS FIG. I is a general block diagram of a synthesizer system of the type disclosed in the above-referenced Schrecongost application. Keyboard produces control signals which are fed via cable to keying circuits I which are regular polyphonic organ tone signal keying circuits. Top octave tone generator generates the highest octave of tone signals which are fed via cable to frequency dividers which comprise parallel chains of frequency dividers to generate other octaves of tone signals to be fed to keying circuits I40. Each of the actuated control elements in keyboard 10 operates one or more individual keying circuits in block I40 to produce polyphonic tone signal outputs on cable as in a regular electronic organ system. Preferably the polyphonic organ system employs large scale integrated circuits to perform the top octave tone generation. frequency division. and DC keying as is characteristic of recent models of organs introduced by Hammond Organ Company. It would also be preferable to employ a separate oscillator and top octave tone generator to feed frequency dividers 120 so that animation of polyphonic organ signals will be independent of animation of monophonic synthesizer signals. US. Pat. No. 3,534.l44 and 3.636.231 disclose integrated circuit approaches to stairstep synthesis keying for formant organ voices and drawbar synthesis keying for sine wave synthesis organ voices.

Keyboard 10 is preferably a single contact per key system and the DC. keying control signals from actuated keys which are fed via cable 20 to organ keying circuits I40 are also sent via cable 40 through low octavc lockout circuit 30 to note collect circuit 60 and octave collect circuit 70 via cable branches 42 and 41. The output signals from note collect circuit 60 are coupled via cable 90 to note perference circuit 160. The output signals from octave collect circuit 70 are fed via cable 50 to low octave lockout circuit 30 and key. octavc preference circuit 190. Signals from octave collect circuit 70 cause low octave lockout circuit 30 to lock out all control signals from keyboard 10 except those corresponding to the highest octave in which keys are actuated. This lockout is effective only for control signals fed to octave collect circuit 70 and note collect circuit 60 and does not affect the transmission of control signals to organ keying circuits 140 because of isolation resistors (not shown) within keyboard 10. As a result of low octave lockout circuit 30 only one octave of keys. namely that of the highest actuated keym is active with respect to the synthesizer portion of the system. This synthesizer system will be described in terms of a high select system which is considered to be more useful when the upper or solo keyboard of an organ is used to control the synthesizer since the melody note is usually the highest note played in polyphonic playing and the synthesizer is essentially a melody instrument. It should be readily apparent that a low select system could be provided for a stand-alone version of the synthcsizer system and would be essentially the reverseof the approach to be described herein. It should also be apparent that a combined low and high select system could also be provided by duplicating the necessary circuitry.

Top octave tone generator 100 generates at least the top octave of twelve tone signals on cable 110. The highest C note may also be generated as a thirteenth tone signal. These tone signals on cable I10 feed note preference circuit which is controlled by signals from note collect circuit 60 to gate onto output lead 161 only the tone signal corresponding to the highest note played in the active octave. Divider I70 divides the tone signal on lead 161 into octavely related tone signals on cable 180. Octave preference circuit I90 functions under the control of signals from octave collect circuit 70 to gate onto lead I91 the appropriate one of the octavely related tone signals from divider corresponding to the octave in which the highest key is actuated. The tone signal on lead 191 thus corresponds to the highest key actuated in the active (highest) octave in which keys are actuated. Low octave lockout circuit 30 prevents any higher key actuated in a lower octave from affecting not preference circuit l6] and thereby precludes erroneous tone signal selection when plural keys in different octaves are actuated.

The high tone signal on lead 191 is fed to pitch and waveform circuits 200 wherein various different pitches may be selected and different waveforms produced. The selected tone signal of selected pitch and waveform is fed to a voltage-controlled filter 210, thence to a voltage-controlled amplifier. and finally to an output speaker system. Pitch and waveform circuits 200, voltage-controlled filter 210, voltage-controlled amplifier 220, top octave tone generator I00, voltagecontroller oscillator 240, vibrato and portamento circuits 250, filter envelope generator 270, amplifier envelope generator 280, legato pulse generator 260, volts per octave circuit 230 and keydown detector 80 are discussed in detail below in conjunction with FIGS. 2-11. FIG. 2 is a specific block diagram of a synthesizer system according to this invention and will be described in reference to FIGS. 3 to II which show specific circuitry for each of the blocks and which are to be assembled according to FIG. 12.

Keyboard 10, octave collect I 70A. keydown detector 80, low octave lockout 30, low note lockout 290, note collect 60, and octave collect 70 are shown in detail in FIG. 5. Keyboard 10 comprises a plurality of keyswitches II coupled to a keying bus 12 to which is applied to -V1 keying potential from a power supply (not shown). Five full octaves of keyswitches are represented by the first and last switch associated with the lowest and highest notes in each octave. Also a siwtch for C6 the 61st note of a console model organ is shown. The number of keyboard octaves is arbitrary.

Cable 21 couples keyswitches II to octave collect circuit 70A which comprises a plurality of diodes D4 which gate all keying signals from keyswitches in the same keyboard octave to a common bus. Low octave lockout circuit 30 receives signals from octave collect circuit to lock out keying signals from all but the highest octave in which keyswitches are actuated in the following manner. A keying signal from the C6 kcyswitch is fed through a diode D4 to a transistor gating circuit 30E. This negative keying signal turns on transistor T5 to a saturate condition to ground out common octave bus 085. The keying signal also is fed via the string of diodes D5 to turn on identical transistor gates in blocks 30A to 30D to ground out common octave busses 081 to 084. The ground reference voltages on these busses are coupled through diodes D7 and cable 41 to the junctions between resistors R9 and diodes D3 associated with the first five keyboard octaves. Consequently any keyswitches actuated in any of those keyboard octaves will be locked out by being shunted to ground. Thus with the C6 keyswitch actuated a keying signal will appear only on common note bus N131 and common octave bus 086.

Similarly. if one of the kcyswitches in the fifth keyboard octave is the highest one actuated a keying signal is coupled via cable 21 a diode D4 into block 30D to turn on atransistor gate and thereby to ground out common octave bus 084. The same keying signal is fed to the left through diodes D5 to gate on transistors in circuits 30A to 30C to ground out common octave busses 081 to 0B3, but the keying signal is blocked from going to the right to turn on transistor T5. Thus, any keyswitchcs in lower keyboard octaves which are actu ated will not produce keying signals on any common note busses. Low octave lockout circuit 30 thus causes only the highest keyboard octave in which notes are played to be active.

Note collect circuit 60 functions to collect all common note keying signals regardless of octave on a common note bus. Diodes D3 coupled between common note keyswitches and common note busses comprise. in effect. multi-input logic OR gates. Note that all C note keyswitches are coupled to common note bus NBl and all B note keyswitches are coupled to common note bus NB12. The same is true for all intermediate notes of the musical scale.

Octave collect circuit 11 70 functions to collect all common octave keying signals on a common octave bus. Thus all keying signals from octave one (C1 to B1) are coupled via cable 41 and diodes D7 to common octave bus 081. All keying signals from octave two are coupled similarly to common octave bus 0B2. and so forth for the rest of the keyboard octaves.

Low note lockout circuit 290 comprises a plurality of transistor gating circuits 290A to 290K. A keying signal on common note bus NB12 from any actuated B note keyswitch is coupled via diode D9 to gating circuit 290K and turns on transistor T4 to saturation which grounds out common note bus N81]. The same keying signal is fed back via the string ofdiodcs D8 to turn on transistors in each of gating circuits 290A to 290.1 andthereby to groundout all common notc busses N81 to NB10. A keying signal on any common note bus thus turns on gating circuits to lock out all keying signals on lower common note busses.

The combined action of low octave lockout circuit 30 and low note lockout circuit 290 is to provide unambiguous high note select whereby only the highest keyswitch actuated will effectively produce a keying signal on related common note and common octave busses. It should be noted that. while the low octave lockout circuit locks out keying signals from all but the high note octave at the input to note collect circuit 60 tc prevent a higher note in a lower octave from acting on low note lockout circuit 290. the low note lockout circuit 290 is D.C. isolated via resistors R9 from low octave lockout circuit 30 and this is required to permit low octave lockout circuit 30 to function when the player changes from a particular note in one octave to a lower note in a higher octave. Under such circumstances. low octave lockout circuit 30 must be able to respond to the lower note in the higher octave to lock out the keyboard octave of the former note. Also keying signals for polyphonic organ keying circuits would be taken directly off the keyswitches to avoid the lockout effects of low octave and low note lockout circuits.

FIG. 6 shows note binary encoder 300, note word latches 310, octave binary encoder 330, and octave word latches 330. Because low octave and low note lockout circuits provide unambiguous high note select and only one keying signal appears on each of the sets of common note and common octave busses. the note and octave keying signals can be encoded into a binary word for storing in note and octave word latches. A keying signal on common note bus N81 is encoded into the binary word 0001 stored in FFNl to FFN4. This results from the encoding through diodes D10 to the set lead S1 of latch FFNl and the reset leads R2 to R4 of latches FFN2 to FFN4. Similar analysis shows that keying signals on common note busses are encoded into binary words according to the following chart:

Common Note Bus FFNl FFNZ FFN3 FFN4 NB] N132 0 0 (l l (l (l N133 l l (l t) N134 l NBS l (l I (l Similarly, keying signals on common octave busses 081 to 086 are encoded into binary words and stored in octave latches FFOl to FF03 as follows:

Common ()ctave Bus F F01 FFOZ F F03 O l (l l (l The diode encode gating to both set and reset leads is preferable to using a common reset signal in a set preference flip-flop" because it avoids any race condition between setting and resetting and ensures prompt. accurate changing of stored binary note and octave words as different notes are played on keyboard 10.

Each of the note latches FFNl to FFN4 (see FIG. 6) and octave latches FFOl to FFOS is a standard bistable flip-flop circuit. A negative keying signal on set lead S1 of note latch FFNl turns on transistor T6 which turns off transistor T7 as the collector of transistor T6 and thus the base of transistor T7 goes to ground. This is the 

1. In a monophonic electronic musical instrument: a plurality of selectably actuable control elements for producing control signals on nOte busses, each control signal element being associated with one note of the musical scale; encoder circuit means for encoding control signals on said note busses into a binary word; memory means for storing said binary word; tone signal generating means for generating tone signals corresponding to notes of the musical scale; and decoder circuit means for decoding said stored binary word to gate a tone signal corresponding to said stored binary word.
 2. Apparatus as claimed in claim 1, further comprising note lockout means for locking out control signals from all but one of a plurality of actuated control elements.
 3. Apparatus as claimed in claim 2, wherein said note lockout means comprises a low note lockout circuit responsive to a control signal on one of said note busses to lock out all control signals from control elements associated with lower notes such that only one of said note busses has a control signal thereon in the event of coincedent actuation of more than one control element; said memory means comprises a plurality of bistable circuits having set and reset input leads and a pair of output leads having opposite logic signals thereon; said encoder circuit means comprises encoding circuit elements connected between each of said note busses and different combinations of said set and reset leads of said bistable circuits to positively determine different combinations of set and reset states of said bistable circuits in response to control signals on different note busses; said tone signal generating means generates said tone signals on separate tone signal busses; and said decoder circuit means comprises decoding circuit elements connected between each of said tone signal busses and different combinations of said output leads of said bistable circuits to gate one tone signal in response to each different combination of set and reset states of said bistable circuits.
 4. A monophonic electronic musical instrument comprising: a plurality of selectively actuable control elements for producing control signals on separate output leads, each control element being associated with a particular note of the musical scale in one of a plurality of octaves; means for collecting control signals associated with common notes in different octaves on common note busses; means for collecting control signals associated with common octaves on common octave busses; tone signal generating means for generating at least the highest octave of tone signals on separate note tone signal busses; octave lockout means for locking out control signals from all but one octave of control elements to determine an active octave; note lockout means for locking out control signals from all but one of a plurality of actuated control elements in said active octave; note gating means for gating one of said tone signals in response to a control signal on an associated common note bus; means for dividing said gated tone signal into octavely related tone signals on octave tone signal busses; and octave gating means for gating one of said octavely related tone signals in response to a control signal on an associated common octave bus.
 5. Apparatus as claimed in claim 4, wherein said note gating means includes a plurality of bistable note storage elements having set and reset input leads and circuit means coupled between each of said common note busses and different combinations of set and reset input leads of said note storage elements to place said note storage elements in different operating states in response to control signals on different common note busses; and said octave gating means includes a plurality of bistable octave storage elements having set and reset input leads and circuit means coupled between each of said common octave busses and different combinations of set and reset leads of said octave storage elements to place said octave storage elements in different operating states in response to control signals on A different common note busses.
 6. Apparatus as claimed in claim 5, wherein the number of said bistable note and octave storage elements corresponds to the corresponding number of common note and common octave busses and said circuit means coupled between corresponding common note and octave busses and associated note and octave storage elements comprises a circuit connection between each said bus and a set lead of its associated storage element and all reset leads of other respective note and octave storage elements such that control signals on individual note and octave busses place one associated note and octave storage elements in a set state and all others in a reset state; and said note and octave gating means each further include a gating element coupled between each respective note and octave storage elements and associated note and octave tone signal busses to gate respective note and octave tone signals in accordance with the operating state of said note and octave storage elements.
 7. Apparatus as claimed in claim 5, wherein the number of said bistable note and octave storage elements corresponds to the number of digits of binary words required to store binary encoded note and octave control signals and said circuit means coupled between corresponding common note and octave busses and note and octave storage elements comprises binary encoding circuit connections between each said bus and a different combination of set and reset leads of associated storage elements to place said storage elements into different combinations of set and reset states; and said note and octave gating means each further include binary decoding gates connected between each respective note and octave tone signal busses and different combinations of output leads from said associated storage elements to gate respective note and octave tone signals in accordance with the combined operating states of said note and octave storage elements.
 8. Apparatus as claimed in claim 7, further comprising at least one tuned circuit means for producing an output signal having a frequency characteristic varying in accordance with a D.C. control signal input; digital-to-analog converter means for generating an analog note position signal from digital note and octave words stored in said note and octave storage elements in accordance with a 1:12 ratio of contributions from words stored in said note and octave storage elements respectively; and means for coupling to said tuned circuit means a D.C. control signal derived from said note position signal.
 9. Apparatus as claimed in claim 8, wherein said digital-to-analog converter means comrises a plurality of current generators gated by respective output signals from associated note and octave storage elements in a set state, said constant current generators associated with said note storage elements generating current levels in the ratios 1:2:4:8 from least to greatest associated binary digits stored therein and said constant current generators associated with said octave storage elements generating current levels in the ratios 12:24:48 from the least to greatest associated binary digits stored therein.
 10. A monophonic electronic musical instrument comprising: a plurality of selectively actuable control elements for producing control signals on separate output leads, each control signal element being associated with a particular note of the musical scale in one of a plurality of octaves; means for collecting control signals associated with common notes in different octaves on common note busses; means for collecting control signals associated with common octaves on common octave busses; tone signal generating means for generating at least the highest octave of tone signals on separate note tone signal busses; octave lockout means for locking out control signals from all but one octave of control elements to determine an active octave; note lockout means for locking out control signals frOm all but one of a plurality of actuated control elements in said active octave; note encoding means for encoding a control signal on one of said common note busses into a binary note word; note storage means for storing said binary note word; note gating means for gating one of said tone signals in accordance with said stored binary note word; means for dividing said gated tone signal into octavely related tone signals on octave tone signal busses; octave encoding means for encoding a control signal on one of said common octave busses into a binary octave word; octave storage means for storing said binary octave word; and octave gating means for gating one of said octavely related tone signals in accordance with said stored binary octave word.
 11. Apparatus as claimed in claim 10, wherein said note gating means comprises a plurality of note decoding gates each coupled to one of said note tone signal busses and responsive to a different binary note word to gate said tone signal thereon; and said octave gating means comprises a plurality of octave decoding gates each coupled to one of said octave tone signal busses and responsive to a different binary octave word to gate said tone signal thereon.
 12. Apparatus as claimed in claim 10, further comprising digital-to-analog decoder means for decoding binary note words and binary octave words in said note and octave storage means into a voltage proportional to the position of the associated note in the associated octave.
 13. Apparatus as claimed in claim 10, wherein said note gating means comprises: a plurality of note D.C. keying circuits each coupled to one of said note tone signal busses; and a plurality of note decoding gates each coupled to one of said note D.C. keying circuits to gate a D.C. keying signal thereto in response to a different binary note word; and said octave gating means comprises: a plurality of octave D.C. keying circuits each coupled to one of said octave tone signal busses; and a plurality of octave decoding gates each coupled to one of said octave D.C. keying circuits to gate a D.C. keying signal thereto in response to a different binary octave word.
 14. Apparatus as claimed in claim 13, further comprising circuit means coupled to said note decoding gates and said octave decoding gates to generate an analog D.C. voltage proportional to the position of the associated note in the associated octave.
 15. A monophonic electronic musical instrument comprising: at least one tuned circuit means for producing an output signal having a frequency characteristic varying in accordance with a D.C. control signal input; a plurality of selectively actuable control elements for producing control signals on separate output leads, each control signal element being associated with a particular note of the musical scale over a plurality of octaves; means for collecting control signals associated with common notes in different octaves on common note busses; means for collecting control signals associated with common octaves on common octave busses; octave lockout means for locking out control signals from all but one octave of control elements to determine an active octave; note lockout means for locking out control signals from all but one of a plurality of actuated control elements in said active octave; note encoding means for encoding a control signal on one of said common note busses into a different binary note word; note storage means for storing said binary note word; octave encoding means for encoding a control signal on one of said common note busses into a different binary octave word; octave storage means for storing said binary octave word; digital-to-analog converter means for generating an analog note position signal from digital note and octave words stored in said note and octave storage elements in accordance with a 1:12 ratio of contributions from words stored iN said note and octave storage elements respectively; and means for coupling to said tuned circuit means a D.C. control signal derived from said note position signal. 